Our long range goal is to understand the role of fetuin in tumorigenesis and metastasis. Fetuin is a approximately 50 kDa serum glycoprotein synthesized primarily by the liver. Its concentration is relatively high in the fetal blood compared to adult blood. Whereas its precise physiological function is not known, it has been shown to be important in bone formation, fetal brain development, and can support the growth of cells in vitro. We have shown that fetuin interacts specifically with matrix metalloproteinases and can activate the zymogen forms of MMP-2 and MMP-9. These enzymes are important in tumorigenesis and metastasis. The central hypothesis of this grant is that fetuin is able to localize matrix metalloproteinases on the surface of tumor cells and can activate the zymogen forms of MMP-2 and MMP-9. These enzymes are important in tumorigenesis and metastasis. The central hypothesis of this grant is that fetuin is able to localize matrix metalloproteinases on the surface of tumor cells and can modulate their activation process. The hypothesis will be tested by three specific aims: 1) Determine the mechanism by which fetuin modulates their activation process. The hypothesis will e tested by three specific aims: 1) Determine the mechanism by which fetuin modulates the activation of matrix metalloproteinases 2) To determine the motifs in fetuins which are responsible for interaction with matrix metalloproteinases and those responsible for cell surface binding and 3) To employ fetuin knockout mice to determine the role of fetuin in tumorigenesis and metastasis. In aim #1, immunoprecipitation and confocal microscopy will be used to colocalize MMP-3 and fetuin on the cell surface. To investigate the modulation of MMP-3 activity by fetuin, BIOTRACT matrix metalloproteinase assay will be used. For specific aim #2, Skatchard assays will be used to study the binding of fetuin to squamous and spindle cell carcinomas. Carbohydrate denuding enzymes will be used to assess the contribution of sugar moieties in the binding interactions.